The invention relates to a safety device for all winches used in various hoisting and load-moving equipment. Such winches are driven by a motor via gears and the control lever is acted upon by the safety device.
A device of the invention is arranged to prevent excessive tension on the cable to be wound on the winch when a load drawn by the winch encounters resistance, this generally occurs at the end of the hoisting movement, and to prevent exaggerated unwinding of the cable when the load is interrupted in its descent by an obstacle, which generally occurs at the end of a downwards movement. A device of the invention may act at any point of the movement of the load if this movement is being impeded in some way, but it has no effect on the functioning of the winch when the load is moving freely.
The prior art in this field is illustrated by the disclosure in French Pat. No. 2,398,689. In this Patent, a safety device for the end of travel is added to the structure of a hoisting apparatus in the path of the metal cable between the winch and a first return pulley for the cable.
It is an object of this invention to provide a safety device which is designed to be combined with a gear and a winch so as to form a complete, compact unit which is independent of the structure of any hoisting apparatus.
Furthermore, in hoisting apparatus of the type comprising a truck moving on a ladder, the ladder often consists of a plurality of sections which slide telescopically into one another. When the ladder is extended by sliding the sections apart, cable has to be supplied progressively, which extends from the winch to the top of the last section of the ladder.
It is a further object of the invention to provide a compact device of the type mentioned hereinbefore which is improved so as to supply successive lengths of metal cable which unroll automatically from the winch as the ladder is extended.